Combustion and detonation development regimes in gas mixtures

Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 5, pp. 72–80, September–October, 1992.     

Effect of a nanosecond gas discharge on deflagration to detonation transition

The possibility of using a high-voltage nanosecond discharge to initiate gaseous detonation was shown experimentally. The experiments were performed with C₃H₈ + 5O₂ and C₃H₈/C₄H₁₀ + 5O₂ + xN₂ (x = 0–10) mixtures at an initial pressure of 0.15–0.6 atm. The discharge was initiated by a voltage pulse of duration ≈60 nsec and amplitude 4–70 kV; the energy input was 0.07–12 J. Under the conditions of the experiment, three flame propagation regimes were observed: slow combustion, transient detonation, and Chapman—Jouguet detonation. For the initiation of the C₃H₈+ 5O₂ mixture in a tube of diameter 140 mm, the length of the deflagration to detonation transition was 130 mm at an initial pressure of 0.3 atm and an initiation energy of 70 mJ. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 80–90, March–April, 2006.     

Conditions of detonation initiation by focusing shock waves in a combustible gas mixture

Based on experiments on focusing shock waves in hydrogen-air mixtures and available publications, the critical shock-wave Mach number at which detonation is initiated near the apex of a concave reflector is analyzed as a function of the reflector size and reactivity of the mixture. The effect of the reflector shape and size on the value of this Mach number is studied. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 6, pp. 84–89, November–December, 2007.     

Reactive impulse from the explosion of a gas mixture in a semiinfinite space

The reactive impulse from the explosion of an acetylene-oxygen mixture in a cylindrical chamber is calculated and measured. The gas mixture was charged into the closed end of the chamber and filled all or part of the length of the chamber. In the latter case, air filled the remaining part of the chamber volume. With a variation in the ratio of chamber and charge lengths from 1 to 7–10, the specific impulse from detonation of the mixture increases from 160 to 500–540 sec. In the case of fuel-air mixtures, the theoretical specific impulse is several times lower per unit mass of the mixture and several times greater per unit mass of the fuel. Lavrent'ev Institute of Hydrodynamics. Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizikia Goreniya i Vzryva. Vol. 30, No. 5, pp. 90–97, September–October, 1994.     

Transition from combustion to detonation in a gaseous hydrocarbon-air mixture

The transition of slow combustion of a hydrocarbon—air mixture to self-sustaining detonation is investigated experimentally in a model tube with the mixture ignited at the closed end. Various mechanisms of the onset of detonation are discussed, along with the transition of the resulting strong detonation to self-sustainment. The influence of a mechanical obstacle placed at the end of the transition zone on the stabilization of the detonation starting point and the shortening of the transition length is investigated.State University, Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 1, pp. 78–86, January–February, 1994.     

Combustion characteristics of coal in a mixture of oxygen and recycled flue gas

The combustion of coal in a mixture of pure O₂ and recycled flue gas is one variant of a novel combustion approach called oxy-fuel combustion. With the absence of N₂, this approach leads to a flue gas stream highly enriched in CO₂. For many applications, this flue gas stream can then be compressed and sequestered without further separation. As a result, oxy-fuel combustion is an attractive way to capture CO₂ produced from fossil fuel combustion. When coal is burned in this O₂ and CO₂ rich environment, its combustion characteristics can be very different from conventional air-fired combustion. In CETC-O, a vertical combustor research facility has been used in the past years to investigate the combustion characteristics of several different coals with this variant of oxy-fuel combustion. This included flame stability, emissions of NO_x, SO_x and trace elements, heat transfer, in-furnace flame profiles and flue gas compositions. This paper will report some of the major findings obtained from these research activities.     

Modeling of reflected waves during detonation of spherical gas mixture volumes

Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 26, No. 3, pp. 82–85, May–June, 1990.     

Combustion gas and NO emission characteristics of hazardous waste mixture particles in a fixed bed

Experiments with fixed-bed incinerators were carried out to model the combustion characteristics and gas emission characteristics of hazardous waste mixture particles in a grate furnace. The results indicate that combustion can be divided into three stages: ignition, main combustion and combustion completion stage. According to the various concentrations of O₂, CO₂ and CO, the main combustion stage can be subdivided into pyrolysis gas combustion and char combustion. Primary air rate, moisture and particle size have significant effects on concentrations of combustion gases and NO. Bed height has no effect on CO₂ concentrations but does have an effect on other combustion gases and NO emissions.     

Simple kinetics and detonation wave structure in a methane-air mixture

A reduced two-stage model of detonation combustion of methane in oxygen and air for equimolar and fuel-lean mixtures is proposed. One-dimensional structures of the detonation wave are calculated for different ratios of the fuel and oxidizer corresponding to the overdriven and Chapman-Jouguet regimes. A comparison of the calculated dependences of the detonation velocity on the methane concentration in the methane-air mixture with available published data reveals their reasonable agreement.